Cooling structure for electric device

ABSTRACT

A cooling structure for an electric device includes an inverter, a plurality of cooling medium paths ( 724 ) through which a cooling medium for the inverter flows, and an inlet ( 722 ) into which the cooling medium to be supplied to the plurality of cooling medium paths ( 724 ) flows. The plurality of cooling medium paths ( 724 ) extend in a direction crossing the aligning direction of the inlet ( 722 ) and the plurality of cooling medium paths ( 724 ). The cooling structure for an electric device further includes a cooling medium distribution mechanism for promoting distribution of the cooling medium to each of cooling medium paths ( 724 ) by suppressing the flow of the cooling medium. The cooling medium distribution mechanism has a flow rate suppression function suppressing the flow rate of the cooling medium flowing through at least one cooling medium path ( 724 ). This flow rate suppression function is realized by a wall ( 726 A,  726 B,  726 C) provided at a cooling medium path ( 724 ).

TECHNICAL FIELD

The present invention relates to a cooling structure for an electric device, particularly, to a cooling structure for an electric device, having a plurality of cooling medium paths.

BACKGROUND ART

There is conventionally known a cooling structure for an electric device, having a cooling medium path (diversion water channel) extending in a direction crossing the flowing direction of the cooling medium from an inlet to the cooling medium path.

For example, U.S. Pat. No. 5,504,378 discloses a direct cooling structure for a switching module having a diversion water channel.

Further, Japanese Patent Laying-Open No. 2004-28403 discloses a cooler for a heating element, having the inlet and outlet of the coolant provided at one side.

In addition, Japanese Patent Laying-Open No. 2005-64382 discloses a cooler for cooling a plurality of electronic components from both sides, having the inlet and outlet of the coolant provided at one side.

In accordance with the cooling structure disclosed in the aforementioned publication of U.S. Pat. No. 5,504,378, the cooling medium may not readily flow to the cooling medium path at a site distant from the inlet of the cooling medium. In this case, the flow of the cooling medium into the plurality of cooling medium paths will vary between each of the cooling medium paths. Although this variation can be suppressed by increasing the width of the cooling medium path located distant from the inlet, the cooling structure will be increased in size thereby.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a cooling structure for an electric device, capable of suppressing variation in the flow rate of a cooling medium at a plurality of cooling medium paths while allowing reduction in size.

A cooling structure for an electric device according to the present invention includes an electric device, a plurality of cooling medium paths through which a cooling medium for the electric device flows, and an inlet into which the cooling medium to be supplied to the plurality of cooling medium paths flows. The plurality of cooling medium paths extend in a direction crossing an aligning direction of the inlet and the plurality of cooling medium paths. The cooling structure for an electric device further includes a cooling medium distribution mechanism to promote distribution of the cooling medium to each cooling medium path by suppressing the flow of the cooling medium.

In accordance with the above-described structure, the flow rate of the cooling medium flowing into the plurality of cooling medium paths can be controlled without excessively increasing the width of the cooling medium path. As a result, variation in the flow rate of the cooling medium at the plurality of cooling medium paths can be suppressed while allowing reduction in the size of the cooling structure for an electric device.

In the cooling structure for an electric device, the cooling medium distribution mechanism preferably has a flow rate suppression function to suppress the flow rate of the cooling medium flowing through at least one cooling medium path.

By selectively providing a cooling medium path having a flow rate suppression function, distribution of the cooling medium can be promoted. Furthermore, by providing a flow rate suppression function in a neighborhood of a site where cooling performance is required, occurrence of a turbulent flow at the site can be promoted in addition to promoting distribution of the cooling medium, leading to improvement of the cooling efficiency.

In the above-described cooling structure for an electric device, the flow rate suppression function is preferably realized by a wall at a cooling medium path provided so as to cross the cooling medium path. Accordingly, a flow rate suppression function can be achieved with a simple structure.

In the above-described cooling structure for an electric device, the wall is preferably provided at each of a plurality of cooling medium paths differing in distance from the inlet. The walls provided at the plurality of cooling medium paths differ in height from each other. Accordingly, the level of flow rate suppression can be altered according to the distance from the inlet. As a result, variation in the flow rate of the cooling medium at the plurality of cooling medium paths can be suppressed.

Preferably, the height of the wall located at a cooling medium path distant from the inlet is relatively low whereas the height of the wall located at a cooling medium path close to the inlet is relatively high. Accordingly, the flow of the cooling medium into a cooling medium path distant from the inlet can be promoted. As a result, variation in the flow rate of the cooling medium at the plurality of cooling medium paths can be suppressed.

Preferably in the above-described cooling structure for an electric device, the wall is provided selectively at a cooling medium path close to the inlet. Accordingly, the flow of the cooling medium into a cooling medium path close to the inlet can be suppressed while the flow of the cooling medium into a cooling medium path distant from the inlet can be promoted. As a result, variation in the flow rate of the cooling medium at the plurality of cooling medium paths can be suppressed.

In the above-described cooling structure for an electric device, the electric device includes, by way of example, an inverter. In this case, the inverter can be cooled efficiently.

In accordance with the present invention, variation in the flow rate of the cooling medium at a plurality of cooling medium paths can be suppressed while allowing reduction in the size of the cooling structure for an electric device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows an example of a configuration of a drive unit including a cooling structure for an electric device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a configuration of a main part of the PCU shown in FIG. 1.

FIG. 3 represents an entire configuration of a cooling structure for an electric device according to an embodiment of the present invention.

FIG. 4 is a plan view of the casing shown in FIG. 3.

FIG. 5 is a sectional view taken along line V-V of FIG. 4.

FIG. 6 is a plan view of a casing in a cooling structure for an electric device according to a comparative example.

BEST MODES FOR CARRYING OUT THE INVENTION

Embodiments of a cooling structure for an electric device according to the present invention will be described hereinafter. The same or corresponding elements have the same reference characters allotted, and description thereof may not be repeated.

FIG. 1 schematically shows an example of a configuration of a drive unit including a cooling structure for an electric device according to an embodiment of the present invention. In the embodiment shown in FIG. 1, a drive unit 1 is incorporated in a hybrid vehicle. A motor generator 100, a housing 200, a reduction gear mechanism 300, a differential mechanism 400, a drive shaft support 500, and a terminal base 600 constitute the drive unit.

Motor generator 100 is a rotating electric machine functioning as an electric motor or a power generator, and includes a rotational shaft 110 attached rotatable with housing 200 via a bearing 120, a rotor 130 attached to rotational shaft 110, and a stator 140.

Rotor 130 includes a rotor core formed of stacked plates of a magnetic substance such as iron, iron alloy, and the like, and permanent magnets embedded in the rotor core. The permanent magnets are arranged equally spaced from each other in the proximity of the outer circumference of the rotor core. The rotor core may be formed of powder magnetic core.

Stator 140 includes an annular stator core 141, a stator coil 142 wound around stator core 141 and a bus bar 143 connected to stator coil 142. Bus bar 143 is connected to a PCU (Power Control Unit) 700 via terminal base 600 provided at housing 200 and a power feed cable 700A. PCU 700 is connected to a battery 800 via a power feed cable 800A. Accordingly, battery 800 is electrically connected with stator coil 142.

Plates of a magnetic substance such as iron, iron alloy, and the like are stacked to constitute stator core 141. On the inner circumferential face of stator core 141 are formed a plurality of tooth sections (not shown) and a slot section (not shown) qualified as a recess between the teeth. The slot section is formed to open at the inner circumferential side of stator core 141. Stator core 141 may be formed of a powder magnetic substance.

Stator coil 142 including the three-phase winding of a U-phase, V-phase and W-phase is wound along the tooth section so as to fit in the slot section. The U-phase, V-phase and W-phase windings of stator coil 142 are wound in a manner deviated from each other on the circumference. Bus bar 143 includes a U-phase, V-phase and W-phase corresponding to the U-phase, V-phase and W-phase of stator coil 142.

Power feed cable 700A is a three-phase cable including a U-phase cable, V-phase cable, and W-phase cable. The U-phase, V-phase and W-phase bus bar 143 is respectively connected to the U-phase cable, V-phase cable and W-phase cable of power feed cable 700A.

The power output from motor generator 100 is transmitted from reduction gear mechanism 300 to drive shaft support 500 via differential mechanism 400. The driving force transmitted to drive shaft support 500 is transmitted to the wheel (not shown) as the torque via a drive shaft (not shown) to drive the vehicle.

In a regenerative braking mode of the hybrid vehicle, the wheel is rotated by the inertia force of the vehicle body. By the torque from the wheel, motor generator 100 is driven via drive shaft support 500, differential mechanism 400, and reduction gear mechanism 300. At this stage, motor generator 100 functions as a power generator. The electric power generated by motor generator 100 is stored in battery 800 via the inverter of PCU 700.

Drive unit 1 is provided with a resolver (not shown) including a resolver rotor and a resolver stator. The resolver rotor is connected to rotational shaft 110 of motor generator 100. The resolver stator includes a resolver stator core and a resolver stator coil wound around the core. By the resolver set forth above, the degree of rotation of rotor 130 of motor generator 100 is detected. The detected degree of rotation is transmitted to PCU 700. PCU 700 generates a drive signal to drive motor generator 100 based on the detected degree of rotation of rotor 130 and the torque command value from an external ECU (Electrical Control Unit) to provide the generated drive signal to motor generator 100.

FIG. 2 is a circuit diagram of a configuration of the main part of PCU 700. Referring to FIG. 2, PCU 700 includes a converter 710, an inverter 720, a control device 730, capacitors C1 and C2, power supply lines PL1-PL3, and output lines 740U, 740V and 740W. Converter 710 is connected between battery 800 and inverter 720. Inverter 720 is connected to motor generator 100 via output lines 740U, 740V and 740W.

Battery 800 connected to converter 710 is a secondary battery such as of nickel hydride, lithium ion, or the like. Battery 800 supplies the generated direct current voltage to converter 710, or is charged by the direct current voltage received from converter 710.

Converter 710 includes power transistors Q1 and Q2, diodes D1 and D2, and a reactor L. Power transistors Q1 and Q2 are connected in series between power supply lines PL2 and PL3, and receive a control signal from control device 730 at the base. Diodes D1 and D2 are connected between the collector and emitter of power transistors Q1 and Q2, respectively, such that current flows from the emitter side to the collector side of power transistors Q1 and Q2, respectively. Reactor L has one end connected to power supply line PL1 that is connected to the positive terminal of battery 800 and the other end connected to the connection node of power transistors Q1 and Q2.

Converter 710 boosts the direct current voltage received from battery 800 by means of reactor L, and supplies the boosted voltage onto power supply line PL2. Converter 710 also down-converts the direct current voltage received from inverter 720 to charge battery 800.

Inverter 720 is formed of a U-phase arm 750U, a V-phase arm 750V and a W-phase arm 750W. Each phase arm is connected in parallel between power supply lines PL2 and PL3. U-phase arm 750U is formed of power transistors Q3 and Q4 connected in series. V-phase arm 750V is formed of power transistors Q5 and Q6 connected in series. W-phase arm 750W is formed of power transistors Q7 and Q8 connected in series. Diodes D3-D8 are connected between the collector and emitter of power transistors Q3-Q8 such that current flows from the emitter side to the collector side of power transistors Q3-Q8, respectively. The connection node of each power transistor of each phase arm is connected to the opposite side of the neutral point of each phase coil of motor generator 100 via output lines 740U, 740V and 740W.

Inverter 720 converts the direct current voltage from power supply line PL2 into alternating current voltage for output to motor generator 100 based on a control signal from control device 730. Inverter 720 rectifies the alternating current voltage generated by motor generator 100 into direct current voltage for output onto power supply line PL2.

Capacitor C1 is connected between power supply lines PL1 and PL3 to smooth the voltage level of power supply line PL1. Capacitor C2 is connected between power supply lines PL2 and PL3 to smooth the voltage level of power supply line PL2.

Control device 730 calculates the voltage of each phase coil of motor generator 100 based on the degree of rotation of the rotor of motor generator 100, the motor torque command value, the current value of each phase of motor generator 100, and the input voltage of inverter 720 to generate, based on the calculated result, a PWM (Pulse Width Modulation) signal for turning on/off power transistors Q3-Q8 and provides the generated signal to inverter 720.

Control device 730 also calculates the duty ratio of power transistors Q1 and Q2 to optimize the input voltage of inverter 720 based on the aforementioned motor torque command value and motor speed to generate, based on the calculated result, a PWM signal that turns on/off power transistors Q1 and Q2, and provides the generated signal to converter 710.

Furthermore, control device 730 controls the switching operation of power transistors Q1-Q8 of converter 710 and inverter 720 in order to convert the alternating current power generated by motor generator 100 into direct current power and charge battery 800.

At PCU 700, converter 710 boosts the direct current voltage received from battery 800 based on a control signal from control device 730 to provide the boosted voltage onto power supply line PL2. Inverter 720 receives the direct current voltage smoothed by capacitor C2 from power supply line PL2 to convert the received direct current voltage into alternating current voltage for output to motor generator 100.

Inverter 720 converts the alternating current voltage generated by the regenerative operation of motor generator 100 into direct current voltage for output onto power supply line PL2. Converter 710 receives the direct current voltage smoothed by capacitor C2 from power supply line PL2 to down-convert the received direct current voltage and charges battery 800.

FIG. 3 shows a configuration of a cooling structure of inverter 720 according to an embodiment of the present invention. FIG. 4 is a plan view of the casing shown in FIG. 3. FIG. 5 is a sectional view taken along line V-V of FIG. 4. In FIGS. 4 and 5, the lid of casing 721 is not shown.

Referring to FIGS. 3-5, casing 721 is a die-cast case formed of, for example, aluminum. A cooling medium such as LLC (Long Life Coolant) flows in casing 721. The cooling medium flows into casing 721 from an inlet 722 in the direction of arrow IN and flows out from casing 721 through outlet 723 in the direction of arrow OUT. The cooling medium flowing out from casing 721 is delivered to a radiator 760 to be cooled. Then, the cooling medium flows into casing 721 again via inlet 722. Thus, cooling of inverter 720 (in FIG. 3, only power transistor Q3 and diode D3 are shown) mounted on casing 721 is promoted. The circulation of the cooling medium is effected by a water pump 770. Coolant water, an anti-freeze fluid, or the like may be used as the cooling medium.

A plurality of cooling medium paths 724 are formed in casing 721. The plurality of cooling medium paths 724 are partitioned by equally spaced fins 725 protruding perpendicular to the mounting face of an electric element. Accordingly, a plurality of cooling medium paths 724 extending in the same direction are provided.

A cooling medium path 724 extends in a direction crossing the flowing direction of the cooling medium (the direction of arrow α in FIG. 4) from inlet 722 towards the plurality of cooling medium paths 724. In the present embodiment, the direction of arrow α is orthogonal to the extending direction of a cooling medium path 724.

Walls 726A, 726B and 726C are provided at cooling medium path 724. Fin 725 and walls 726A, 726B and 726C are formed integrally with casing 721.

FIG. 6 is a plan view of a cooling structure for an electric device according to a comparative example. Referring to FIG. 6, the aforementioned walls are not provided in the comparative example. In this case, the cooling medium readily flows to a cooling medium path 724 located close to inlet 722 (region A in FIG. 6), but not readily to cooling medium path 724 located distant from inlet 722 (region B in FIG. 6). Therefore, there are concerns about degradation in the cooling performance of inverter 720 due to variation in the flow rate of the cooling medium between the plurality of cooling medium paths 724.

In contrast, the cooling structure according to the present embodiment has wall 726A formed higher than wall 726B, and wall 726B formed higher than wall 726C, as shown in FIGS. 4 and 5. In other words, the height of the wall distant from inlet 722 is set relatively low. A wall is not provided at the most remote region from inlet 722. Thus, the flow of the cooling medium to a cooling medium path 724 distant from inlet 722 can be promoted while the flow of the cooling medium to a cooling medium path 724 located close to inlet 722 is regulated. As a result, variation in the flow rate of the cooling medium at a plurality of cooling medium paths 724 can be suppressed.

Provision of walls 726A, 726B and 726C set forth above promotes formation of a turbulent flow at the downstream side of walls 726A, 726B and 726C. It is expected that the cooling performance can be improved.

Although the height of each of walls 726A, 726B and 726C is constant along the direction of width entirely in the embodiment of FIGS. 4 and 5, the height of each of walls 726A, 726B and 726C may be reduced with distance from inlet 722.

In recapitulation, the cooling structure for an electric device according to the present embodiment includes an inverter 720 qualified as “electric device”, a plurality of cooling medium paths 724 through which a cooling medium for inverter 720 flows, and an inlet 722 into which the cooling medium to be supplied to the plurality of cooling medium paths 724 flows. The plurality of cooling medium paths 724 extend in a direction crossing the aligning direction of inlet 722 and cooling medium paths 724. The cooling structure for an electric device further includes a cooling medium distribution mechanism for promoting distribution of the cooling medium to each of cooling medium paths 724 by suppressing the flow of the cooling medium. Specifically, the cooling medium distribution mechanism includes a flow rate suppression function suppressing the flow rate of the cooling medium flowing through at least one cooling medium path 724. This flow rate suppression function is realized by walls 726A, 726B and 726C at cooling medium paths 724, each provided to cross cooling medium path 724. Thus, a flow rate suppression function can be achieved by a simple structure set forth above.

Walls 726A, 726B and 726C are provided at the plurality of cooling medium paths 724 differing in distance from each other from inlet 722. Further, walls 726A, 726B and 726C differ in height from each other. Specifically, the height of wall 726C located at cooling medium path 724 distant from inlet 722 is relatively low whereas the height of wall 724A located at cooling medium path 724 close to inlet 722 is relatively high.

By differentiating the height of walls 726A, 726B and 726C as set forth above, the level of suppressing the flow rate can be altered according to the distance from inlet 722. Specifically, by setting the height of wall 726A located close to inlet 722 high and the height of wall 726C distant from inlet 722 low, the flow of the cooling medium to a cooling medium path 724 distant from inlet 722 can be promoted.

Furthermore, the aforementioned wall is not provided at cooling medium path 724 located farthest from inlet 722. In other words, walls 726A, 726B and 726C are selectively provided at cooling medium path 724 close to inlet 722. Accordingly, the flow of the cooling medium to cooling medium path 724 located distant from inlet 722 can be promoted while the flow of the cooling medium to cooling medium path 724 located close to inlet 722 is suppressed.

In the present embodiment, distribution of the cooling medium is promoted by altering the height of walls 726A, 726B and 726C. However, distribution of the cooling medium can be promoted with the height of walls set constant by selectively forming a hole in wall 726C located distant from inlet 722, or by forming different sizes of holes in all walls 726A, 726B and 726C (specifically, the hole at wall 726A is relatively small whereas the hole at wall 726C is relatively large).

In accordance with the cooling structure of the present embodiment, the flow rate of the cooling medium flowing into a plurality of cooling medium paths 724 can be controlled without excessively increasing the width of cooling medium path 724. As a result, variation in the flow rate of the cooling medium at a plurality of cooling medium paths 724 can be suppressed while allowing reduction in the size of the cooling structure for inverter 720.

It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The technical range of the present invention is defined by the appended claims, and all changes that fall within limits and bounds of the claims, or equivalent thereof are intended to be embraced by the claims.

INDUSTRIAL APPLICABILITY OF THE INVENTION

The present invention is applicable to a cooling structure for an electric device such as an inverter. 

1. A cooling structure for an electric device, comprising: an electric device including a plurality of electric elements, a casing on which said plurality of electric elements are mounted, a plurality pf cooling medium paths, formed in said casing, through which a cooling medium for said electric device flows, and an inlet into which said cooling medium to be supplied to said plurality of cooling medium paths flows, said plurality of cooling medium paths extending in a direction crossing an aligning direction of said inlet and said plurality of cooling medium paths, said cooling structure for an electric device further comprising: a cooling medium distribution mechanism promoting distribution of the cooling medium to each of said cooling medium paths by suppressing a flow of the cooling medium, said cooling medium distribution mechanism having a flow rate suppression function to suppress a flow rate of the cooling medium flowing through at least one said cooling medium path, and a level of suppressing the flow rate at said plurality of coolant medium paths being altered such that a flow of said cooling medium into said cooling medium path located relatively distant from said inlet is relatively promoted while the flow of said cooling medium into said cooling medium path located relatively close to said inlet is relatively suppressed.
 2. (canceled)
 3. The cooling structure for an electric device according to claim 1, wherein said flow rate suppression function is realized by a wall at the cooling medium path provided so as to cross said cooling medium path.
 4. The cooling structure for an electric device according to claim 3, wherein said wall is selectively provided at said cooling medium path located close to said inlet.
 5. A cooling structure for an electric device, comprising: an electric device, a plurality of cooling medium paths through which a cooling medium for said electric device flows, and an inlet into which said cooling medium to be supplied to said plurality of cooling medium paths flows, said plurality of cooling medium paths extending in a direction crossing an aligning direction of said inlet sand said plurality of cooling medium paths, said cooling structure for an electric device further comprising: a cooling medium distribution mechanism promoting distribution of the cooling medium to each of said cooling medium paths by suppressing a flow of the cooling medium, said cooling medium distribution mechanism having a flow rate suppression function to suppress a flow rate of the cooling medium flowing through at least one of said cooling medium path, said flow rate suppression mechanism being realized by a wall at a cooling medium path provided so as to cross said cooling medium path, said wall being provided at each of said plurality of cooling medium paths differing in distance from each other from said inlet, and the walls provided at said plurality of said cooling medium paths differing in height from each other.
 6. The cooling structure for an electric device according to claim 5, wherein the height of said wall located at said cooling medium path distant from said inlet is relatively low, and the height of said wall located at said cooling medium path close to said inlet is relatively high.
 7. The cooling structure for an electric device according to claim 1, wherein said electric device includes an inverter.
 8. The cooling structure for an electric device according to claim 5, wherein said electric device includes an inverter. 